Stability of emulsions for parenteral feeding: Preparation and characterization of o/w nanoemulsions with natural oils and Pluronic f68 as surfactant

For hydrophobic bioactive compounds, poor water solubility is a major limiting factor for their use in different applications in the field of food industry or pharmacy. For this reason they are administrated as emulsions, in which the substance is dissolved in an organic compound, which is dispersed in an aqueous phase as droplets stabilized by a surfactant. It has been demonstrated that the colloidal stability of the nanoemulsion formulations can be precisely controlled by the chemical structure of the interface. In this paper, a promising delivery system has been studied. As surfactant, we have used the amphiphilic uncharged tri-block copolymer Pluronic F68, and natural oils from soybean, sesame and olive as the organic phase. The nanoemulsions were prepared by ultrasonication, and their stability at different synthesis conditions such as ultrasound power and surfactant concentration has been studied by monitoring backscattering using a Turbiscan. The more stable emulsions have been characterized by DLS, and their droplet size was below 500 nm, which has resulted very appropriate for parenteral administration. A destabilization of the system always takes place above certain surfactant concentration. This phenomenon was described as a depletion–flocculation effect caused by non-adsorbed micelles. This destabilization was modelled by adding to the DLVO interaction energy a contribution addressing the force between two spherical particles in the presence of non-adsorbing spherical macromolecules.